Bipolar ECG Research Articles

Improved recording of atrial activity by modified bipolar leads derived from the 12-lead electrocardiogram

This study investigates the use of multivariate linear regression to estimate three bipolar ECG leads from the 12-lead ECG in order to improve P-wave signal strength. The study population consisted of body surface potential maps recorded from 229 healthy subjects. P-waves were then isolated and population based transformation weights developed. A derived P-lead (measured between the right sternoclavicular joint and midway along the costal margin in line with the seventh intercostal space) demonstrated significant improvement in median P-wave root mean square (RMS) signal strength when compared to lead II (94μV vs. 76μV, p<0.001). A derived ES lead (from the EASI lead system) also showed small but significant improvement in median P-wave RMS (79μV vs. 76μV, p=0.0054). Finally, a derived modified Lewis lead did not improve median P-wave RMS when compared to lead II. However, this derived lead improved atrioventricular RMS ratio. P-wave leads derived from the 12-lead ECG can improve signal-to-noise ratio of the P-wave; this may improve the performance of detection algorithms that rely on P-wave analysis.

Development of a portable wireless system for bipolar concentric ECG recording

Cardiovascular diseases (CVDs) remain the biggest cause of deaths worldwide. ECG monitoring is a key tool for early diagnosis of CVDs. Conventional monitors use monopolar electrodes resulting in poor spatial resolution surface recordings and requiring extensive wiring. High-spatial resolution surface electrocardiographic recordings provide valuable information for the diagnosis of a wide range of cardiac abnormalities, including infarction and arrhythmia. The aim of this work was to develop and test a wireless recording system for acquiring high spatial resolution ECG signals, based on a flexible tripolar concentric electrode (TCE) without cable wiring or external reference electrode which would make more comnfortable its use in clinical practice. For this, a portable, wireless sensor node for analogue conditioning, digitalization and transmission of a bipolar concentric ECG signal (BC-ECG) using a TCE and a Mason-likar Lead-I ECG (ML-Lead-I ECG) signal was developed. Experimental results from a total of 32 healthy volunteers showed that the ECG fiducial points in the BC-ECG signals, recorded with external and internal reference electrode, are consistent with those of simultaneous ML-Lead-I ECG. No statistically significant difference was found in either signal amplitude or morphology, regardless of the reference electrode used, being the signal-to-noise similar to that of ML-Lead-I ECG. Furthermore, it has been observed that BC-ECG signals contain information that could not available in conventional records, specially related to atria activity. The proposed wireless sensor node provides non-invasive high-local resolution ECG signals using only a TCE without additional wiring, which would have great potential in medical diagnosis of diseases such as atrial or ventricular fibrillations or arrhythmias that currently require invasive diagnostic procedures (catheterization).

A Low Latency Electrocardiographic QRS Activity Recovery Technique for Use on the Upper Left Arm

Empirical mode decomposition is used as a low latency method of recovering the cardiac ventricular activity QRS biopotential signals recorded from the upper arm. The recovery technique is tested and compared with the industry accepted technique of signal averaging using a database of “normal” rhythm traces from bipolar ECG leads along the left arm, recorded from patient volunteers at a cardiology day procedure clinic. The same partial recomposition technique is applied to recordings taken using an innovative dry electrode technology supplied by Plessey Semiconductors. In each case, signal to noise ratio (SNR) is used as a metric for comparison.

Diseño y Construcción de un Prototipo de Electrocardiografía Dinámica “Holter” Universal de Tres Canales con Interfaz Electrónica para Cualquier Plataforma de Instrumentación Virtual

This paper describes the design and construction of a portable electrocardiogram (Holter) for the acquisition and storage of the first and second bipolar derivation ECG and precordial lead. The prototype built has the advantage over similar commercial equipment, that downloads the stored signals in analog form, which lets you use any virtual instrumentation platform, such as LabVIEW, BIOPAC or otherwise, and does not rely on communication protocols. The output signals of the Holter, were compared with the input provided by an ECG patient simulator, where he found a great similarity in the amplitudes, shapes, and frequency spectrum without varying the heart rate, the signal of interest study by cardiologist in case of patients with arrhythmias.

Research on Heart Rate Detection Algorithm Based on Bipolar Movement ECG Signals

Abstract The heart rate indicates the important indicator of the movement and physical body enginery, so this paper design and use the bi-polar ECG signal collection system. The traditional method to accurately get the heart rate from the bi-polar ECG information under the movement status is not very effective. Two mainstream time-domain—frequency-domain analysis method is used to analyze and compare the ECG signals. The results indicate that the discrete wavelet transfer can effectively recover the heart rate information from the ECG information with noises. After discrete wavelet transfer and reestablishment, the heart rate can be accurately computed.

Altered Interatrial Conduction Detected in MADIT II Patients Bound to Develop Atrial Fibrillation

Changes in P-wave morphology have recently been shown to be associated with interatrial conduction route used, without noticeable changes of P-wave duration. This study aimed at exploring the association between P-wave morphology and future atrial fibrillation (AF) development in the Multicenter Automatic Defibrillator Trial II (MADIT II) population. Patients included in MADIT-II without a history of AF with sinus rhythm at baseline who developed AF during the study ("Pre-AF") were compared to matched controls without AF development ("No-AF"). Patients were followed for a mean of 20 months. A 10-minute high-resolution bipolar ECG recording was obtained at baseline. Signal-averaged P waves were analyzed to determine orthogonal P-wave morphology, P-wave duration, and RMS20. The P-wave morphology was subsequently classified into one of three predefined types using an automated algorithm. Thirty patients (age 68 +/- 7 years) who developed AF during MADIT-II were compared with 60 patients (age 68 +/- 8 years) who did not. P-wave duration and RMS20 in the Pre-AF group was not significantly different from the No-AF group (143 +/- 21 vs 139 +/- 30 ms, P=0.26, and 2.0 +/- 1.3 vs 2.1 +/- 1.0 muV, P=0.90). The distribution of P-wave morphologies was shifted away from Type 1 in the Pre-AF group when compared to the No-AF group (Type 1/2/3/atypical; 25/60/0/15% vs 10/63/10/17%, P=0.04). This study is the first to describe changes in P-wave morphology in patients prior to AF development. The results indicate that abnormal interatrial conduction may play a role in AF development in patients with prior myocardial infarction and congestive heart failure.

Prolonged QT Interval Is Associated with Blood Pressure Rather Than Left Ventricular Mass in Spontaneously Hypertensive Rats

QT interval is prolonged in hypertensive individuals, although the factors responsible for this increase are not completely understood. We questioned whether enhanced left ventricular mass (LVM) or increased systemic blood pressure represents the principal factor determining QT prolongation in the period of development of hypertension and left ventricular hypertrophy (LVH) in spontaneously hypertensive rats (SHR). In 12-and 20-week-old SHR (SHR12 and SHR20) and age-matched normotensive Wistar-Kyoto rats (WKY12 and WKY20), arterial systolic blood pressure (sBP) was measured using tail-cuff technique. Orthogonal Frank ECG was registered in anaesthetized animals in vivo, and bipolar ECG was measured in spontaneously beating isolated hearts in vitro. Progressive increase of sBP and LVM resulted in significant QT prolongation in SHR20 as compared to WKY12, WKY20, and also to SHR12 in vivo (WKY12: 82 ± 9 ms, WKY20: 81 ± 9 ms, SHR12: 88 ± 15 and SHR20: 100 ± 10, respectively; p < 0.05) but not in isolated hearts (WKY20: 196 ± 39 ms and SHR20: 220 ± 55, respectively; NS). In whole animals, QT duration was positively related to sBP (r = 0.6842; p < 0.001) but not to LVM (r = 0.1632, NS) in SHR20. The results suggest that QT prolongation in SHR developing hypertension and LVH depends on blood pressure rather than increase in LVM. In this period, myocardial hypertrophy is probably the predisposition for QT prolongation, but the significant change manifests only in the presence of elevated systemic factors.

Database testing of a subcutaneous monitor with wireless alarm

Abstract We have tested the accuracy of detection of cardiac arrest in a cardiac event recorder that has the 4x4cm sensor implanted, the recorder external, and the two connected by wireless. Storage and transmission is activated by the patient when symptoms are present or automatically when cardiac arrest is detected, in which case the recorder sounds a loud alarm to alert bystanders. It is the automatic mode that requires database testing of accuracy. Materials We obtained an appropriate database by mapping the chest in 60 ICD patients in sinus rhythm (SR) and induced ventricular fibrillation (VF), and deriving bipolar ECGs from adjacent electrodes located where the electrodes on the subQ sensor would be. (We then implanted the device in 2 dogs and demonstrated the equivalence of ECGs recorded on the skin to subcutaneous ECGs). A blinded selection of 10 of these 60 patients, together with 14 records from the MIT/BIH database, formed a testing set; the others were available for development and training of the detection algorithm. Results In all 60 patients, ECGs from closely-spaced electrodes properly located on the chest appeared suitable for automatic VF detection. Formal testing with the 24-patient database yielded sensitivity and specificity of 100% in detecting VF. Conclusion It appears a 4cm square subcutaneous sensor with electrodes at its corners can reliably monitor cardiac activity, accurately detect the occurrence of cardiac arrest, transmit the ECG to an external receiver, and produce an alarm when a life-threatening arrhythmia is detected.

AHA/ACCF Scientific Statement on the Evaluation of Syncope

AHA/ACCF Scientific Statement on the Evaluation of Syncope

Assessment of drug-induced QT interval prolongation in conscious rabbits

Introduction Most preclinical trials are designed to identify potential torsadogenicity test only for surrogates of torsade de pointes, most commonly prolongation of the heart rate corrected QT interval (QTc). This study was conducted to determine which correction method best accounts for the effects of changes in the RR interval on the QT interval of conscious rabbits. This study was also conducted to validate the use of conscious, sling-trained rabbits to assess the QTc interval, and to evaluate the reliability and accuracy of this preparation in predicting drug-induced QTc prolongation in humans. Methods ECGs were recorded via bipolar transthoracic ECG leads in 7 conscious rabbits previously trained to rest quietly in slings. The heart rate was slowed with 2.0 mg/kg zatebradine to assess the effects of heart rate on the QT interval. The same ECG and sling preparation was used to evaluate the effects in of three drugs known to be torsadogenic in humans (cisapride, dofetilide and haloperidol), two drugs known to be non-torsadogenic in humans (propranolol and enalaprilat) and a control article (vehicle). All of the test articles were administered intravenously to 4 rabbits, and both RR and QT intervals were measured and the corrected QT values were calculated by an investigator blinded to the test article, utilizing our own algorithm (QTc = QT / (RR) 0.72) which permitted the least dependency of QTc on RR interval. Results The following regression equations were obtained relating QT to RR: QT = 2.4RR 0.72, r 2 = 0.79, with RR intervals varying between 210 and 350 ms. QTc lengthened significantly in all conscious rabbits given intravenous cisapride, dofetilide and haloperidol ( p < 0.05), and QTc did not change with DMSO (vehicle control), propranolol or enalaprilat. Discussion Results indicate that a bipolar transthoracic ECG recorded in conscious, sling-trained rabbits may provide an easy and economical methodology useful in predicting QTc lengthening of novel pharmacological entities.

Avian echocardiography

Abstract Echocardiography in birds is a useful intravitam technique for morphological and functional cardiac assessment, although the technical equipment has to be advanced to examine the avian heart. Probes with small coupling surfaces and frequencies of at least 7.5 MHz are necessary, and ultrasound devices should be able to produce at least 100 frames/s. A bipolar ECG is used to examine the heart in endsystolic and enddiastolic stage. Two approaches for coupling the probe are described. By using the ventromedian approach, two horizontal longitudinal views present the chambers, the interventricular septum, and the valves of the heart. Reference values for B-Mode and spectral Doppler are available for different species, but experiences with Doppler examinations in diseased birds are still rare. Common pathological echocardiographic findings in birds are hydropericardium, hypertrophy and/or dilation of the right ventricle, and hypertrophy of the muscular right atrioventricular valve.

Electrocardiograms in selected species

The electrocardiogram, or ECG, is the recording of the electrical activity of the heart from electrodes placed on the surface of the body. The recorded electrical activity results from the depolarization of the individual cardiomyocytes that give rise to small extracellular potential changes. When two electrodes (referred to as a lead) are attached to the body surface, a circuit is formed, and by using an amplifier and a voltage meter, the changes in voltage between these two electrodes can be measured. When these signals are recorded continuously as voltage against time the (bipolar) ECG is formed. In every lead, one electrode is designated the positive side and the remaining electrode(s) as the negative side. By definition, all deflections toward the positive pole are recorded as positive, or upward, deflections and those away from this pole are recorded as negative, or downward, deflections. The movement of electrical charges in the heart is a three-dimensional event, and the net resulting charge at any moment in the cardiac cycle can be represented by a vector, with both a direction and a magnitude. This cardiac vector is represented by an arrow that describes these characteristics: the direction is represented in the shaft’s direction, the polarity with the arrow head and the magnitude with the shaft’s length. The surface ECG is therefore the projection of the cardiac vector in a plane determined by the position of the electrodes. For example, if the electrodes are placed on both front limbs and the left hind limb the ECG measured between these electrodes corresponds to the frontal plane leads I, II, and III.

Sympathetic reinnervation after heart transplantation, assessed by iodine-123 metaiodobenzylguanidine imaging, and heart rate variability.

Complete allograft denervation occurs during heart transplantation. Partial ventricular sympathetic reinnervation may develop one year or later after transplantation and can be measured with iodine-123-meta-iodobenziylguanidine (MIBG) uptake. Aim of this study was to assess sinus node sympathetic reinnervation measured with heart rate variability and ventricular sympathetic reinnervation evaluated with MIBG. Twelve patients and 14 healthy controls were included. In patients, MIBG scintigraphy with early and late imaging was performed. Heart to mediastinum ratio (HMR) was calculated and patients were divided in groups with (HMR>1.3) and without left ventricular reinnervation (HMR<1.3). Bipolar ECG with high sampling rate and resolution was recorded over 8.5 min in supine position and in upright position after 10 min interval. R-R intervals in time domain and heart rate variability in frequency domain through spectral power analysis of R-R intervals were analysed to evaluate sinus node reinnervation. Spectral power in low frequency range (0.04-0.15 Hz) above 4.5 ms(2) was considered as sinus node sympathetic reinnervation. Six (50%) patients had evidence of left ventricular sympathetic reinnervation on scintigraphy. Sinus node sympathetic reinnervation based on heart rate variability was detected in 6 (50%) patients in supine, and in 4 (33%) patients in upright body position. Four patients groups were discerned: (1) with ventricular and sinus node sympathetic reinnervation, (2) with sinus node sympathetic reinnervation, (3) with ventricular sympathetic reinnervation and (4) without atrial or ventricular sympathetic reinnervation. Ventricular reinnervation process was time dependent and sinus node reinnervation was not. Simultaneous ventricular sympathetic reinnervation assessed by MIBG and sinus node sympathetic reinnervation assessed by heart rate variability in supine as in upright position were detected only in two patients (17%). The results of our study show that eventual sinus node sympathetic reinnervation and left ventricular sympathetic reinnervation do not occur simultaneously.

Analysis of electrocardiograms for subcutaneous monitors

We are developing a subcutaneous cardiac arrest monitor and alarm with electrodes that have spacing of a few centimeters. We hypothesize that closely spaced bipolar electrodes that provide QRS amplitudes of a millivolt or more in sinus rhythm (SR) will not provide similar amplitudes during ventricular tachyarrhythmia (VT/VF), and that an orthogonal set of electrode pairs in diagonal is necessary to produce signals of sufficient amplitude in order to distinguish these rhythms. Methods: Forty patients were studied during ICD implantation in the clinical electrophysiology laboratory. A square array of 9 electrodes with 4- to 10-cm spacing between adjacent electrodes was placed on the patient’s anterior chest over the left heart. The center electrode in the left most column is located in the 5th intercostal space at the left sternal border. Eight-channel recordings were made in SR and during induced VT/VF from the 8 peripheral electrodes referenced to the central member of the array. From these recordings all 20 bipolar ECGs of adjacent (including diagonally adjacent) electrodes were constructed algebraically. QRS peak-peak amplitudes in SR and VT/VF were measured in each bipolar lead and in the spatial vector formed by summing the squares of each adjacent and orthogonal pair of these leads. Results: Electrode pairs that yielded optimal ECG amplitudes in SR were not always the pairs that yielded optimal amplitudes in VT/VF. But in every patient two orthogonal pairs could be found whose QRS vector amplitude is sufficient in both SR and VT/VF to separate the rhythms. Conclusions: A patient-defined set of bipolar electrode pairs is suitable for automatic separation of SR and VT/VF by rate in subcutaneous ambulatory monitoring.

QT and RR Intervals in Conscious and Anesthetized Guinea Pigs with Highly Varying RR Intervals and Given QTc-Lengthening Test Articles

A facile system for obtaining electrocardiograms from conscious animals was used to conduct studies on 12 animals studied both conscious and anesthetized, on 4 conscious animals given vehicle (0.5% methylcellulose) and QT-lengthening test articles, and on 6 animals given test articles thought to not lengthen QTc. In 12 animals whose ECGs were monitored via a bipolar transthoracic ECG, heart rates were slowed with 1.0 mg/kg zatebradine, while they were conscious in their slings, and after being anesthetized with ketamine/xylazine. The following regression equations were obtained relating QT to RR: QT = 44.7 ln RR - 132.9, r2 = 0.7, for conscious animals; QT = 79.4 ln RR - 287.4, r2 = 0.8 for anesthetized animals, with RR intervals varying between 150 and 550 ms. The anesthetic increases QT at all RR intervals (p < 0.001), but does not change the slope of the relationship between QT and RR when compared with the conscious guinea pig. The Fridericia method was best for correcting QT for RR interval in conscious guinea pigs, but the Bazett method was best for correcting in anesthetized animals. QTc lengthened significantly in all conscious guinea pigs given, orally, cisapride, ketoconazole, and sotalol (positive test articles) and did not change with methylcellulose (the vehicle) or with propranolol, verapamil, or enalapril (negative controls). These techniques and relationships demonstrate that this methodology may be useful in exploring torsadogenic effects of novel pharmacological entities.

Differences in coupling interval‐dependent effects of sotalol on infarcted and noninfarcted areas of dog hearts after myocardial infarction

AbstractWe examined the coupling interval‐dependence of the effects of sotalol (dl‐sotalol) on effective refractory periods (ERPs) and epicardial activation in ventricles of dog hearts after myocardial infarction, and clarified their differences between infarcted and noninfarcted areas. Myocardial infarction was produced by the two‐stage ligation of left anterior descending coronary artery in dogs. At 7 to 9 days after ligation, bipolar electrodes were sutured on the ventricular surface of the noninfarcted and the infarcted areas. Single (S1) or double (S1/S2) electrical stimulations with various coupling intervals were applied on the ventricle during atrial pacing. S1 was triggered by a prior R wave of pacing rhythm with coupling interval of 300 ms (S1[300]) or 180 ms (S1[180]). Coupling intervals of S1 and S2 were between 250 and 130 ms. ERPs, activation delay, and functional refractory periods (FREPs) in ventricles were measured after S1(180) or S1(300). Ventricular activation delay was a time interval from the artifact of S1 or S2 to the most delayed measurable wave. The coupling interval of S1–S2 was 170 or 160 ms. RT intervals were measured in the bipolar ECGs after S1(300) or S1(180). Sotalol was administered intravenously in dosages of 2, 4, and 8 mg/kg. Sotalol prolonged the ERPs in noninfarcted areas in a lesser extent after S1(180) than after S1(300), whereas in infarcted areas the ERP prolongation was in a similar extent after S1(180) and S1(300). Sotalol prolonged the RT intervals in a lesser extent after S1(180) than after S1(300) in noninfarcted areas, but in a similar extent after S1(180) and after S1(300) in infarcted areas. FERPs were also prolonged by sotalol in infarcted areas in a similar extent after S1(180) and after S1(300). Sotalol prolonged ventricular activation delay after S1/S2 in the infarcted areas, which was greater after S1/S2(180/170) than after (300/170). Delayed activation was blocked more frequently after the S1/S2(180/160) than after S1/S2(300/160). These results indicate that the effects of sotalol on ventricular activation delay are reverse‐use dependent in noninfarcted areas but use‐dependent in infarcted areas, which may contribute to suppression of ventricular tachyarrhythmias in patients with coronary heart disease. Drug Dev. Res. 58:258–267, 2003. © 2003 Wiley‐Liss, Inc.

Dispersion of cell-to-cell uncoupling precedes low K+-induced ventricular fibrillation

We hypothesize that hypokalemia-related electrolyte imbalance linked with abnormal elevation of intracellular free Ca2+ concentration can cause metabolic disturbances and subcellular alterations resulting in intercellular uncoupling, which favor the occurrence of malignant arrhythmias. Langendorff-perfused guinea pig heart (n = 44) was subjected to a standard Tyrode solution (2.8 mmol/l K+) followed by a K+-deficient solution (1.4 mmol/l K+). Bipolar ECG of the left atria and ventricle was continuously monitored and the incidence of ventricular fibrillation was evaluated. Myocardial tissue sampling was performed during stabilization, hypokalemia and at the onset of fibrillation. Enzyme activities of succinic dehydrogenase, glycogen phosphorylase and 5-nucleotidase were determined using in situ catalytic histochemistry. The main gap junction protein, connexin-43, was labeled using mouse monoclonal antibody and FITC conjugated goat antimouse antibody. Ultrastructure was examined by transmission electron microscopy. The free Ca2+ concentration was measured by the indo-1 method in ventricular cell cultures exposed to a K+-free medium. The results showed that sustained ventricular fibrillation appeared within 15-30 min of low K+ perfusion. This was preceded by ectopic activity, episodes of bigeminy and tachycardia. Hypokalemia induced moderate reversible and sporadically irreversible subcellular alterations of cardiomyocytes and impairment of intercellular junctions, which were heterogeneously distributed throughout myocardium. Patchy areas with decreased enzyme activities and diminished immunoreactivity of connexin-43 were found. Furthermore, lack of external K+ was accompanied by an increase of intracellular Ca2+. The prevention of Ca2+ overload by either 1 mmol/l Ni2+ (Na+/Ca2+ inhibitor), 2.5 mmol/l verapamil, 10 mmol/l d-sotalol or 10 mmol/l tedisamil was associated with the protection against fibrillation. The results indicate that hypokalemia induces Ca2+ overload injury and disturbances in intercellular coupling. Dispersion of these changes throughout the myocardium may serve as the basis for microreentry circuits and thus favor fibrillation occurrence.

QT dispersion from body surface ECG does not reflect the spatial dispersion of ventricular repolarization in sheep.

The correlation between the QT dispersion on body surface ECG and the dispersion in ventricular repolarization from the cardiac surface was studied in six sheep anesthetized with pentobarbital. The standard 12-lead body surface ECG and multiple ventricular epicardial ECGs were simultaneously recorded. The activation-recovery interval (ARI) was measured from the unipolar epicardial ECGs. The pooled QT dispersion from the six animals was significantly smaller than the pooled ARI dispersion (22.7 +/- 2.6 vs 33.0 +/- 6.9 ms, P < 0.01). There was no correlation between the QT and ARI dispersion. The unipolar epicardial ECGs were then converted into bipolar ECGs and epicardial QT intervals were subsequently acquired from these ECGs. The average value of epicardial QT dispersion from the six animals was similar to that of body surface ECG, but was less than the ARI dispersion (27.5 +/- 6.8 vs 33.0 +/- 6.9, P < 0.01). A good correlation between the epicardial QT dispersion and ARI dispersion was identified (r = 0.84, P < 0.05). In addition, a prolongation in ventricular repolarization, induced by an increase in coronary flow, elicited a pooled ARI dispersion of 62.3 +/- 6.2 ms (n = 6), which was larger than the simultaneously recorded body surface QT dispersion (28.3 +/- 9.8 ms, n = 6, P < 0.01). No correlation between the ARI and QT dispersion was found in the presence of the prolonged ventricular repolarization. In conclusion, QT dispersion from a 12-lead body surface ECG seems to underestimate the spatial dispersion of ventricular repolarization acquired from sheep epicardium.

Multipolar endocardial mapping of the right heart using a basket catheter: acute and chronic animal studies.

The development of catheter-based ablative techniques for primary atrial and ventricular arrhythmias is likely to be assisted by improved techniques for systematic endocardial activation sequence mapping. RA mapping using a multielectrode basket catheter has been shown to be feasible with minimal acute toxicity in a prior study. The objectives of the current study are to investigate: (1) the utility of the basket catheter for mapping RV activation; and (2) the evolution of acute endocardial lesions produced by basket catheter use in both the RA and RV over 4-8 weeks time. A flexible, 5-spoke basket catheter bearing 25 electrode pairs was placed in the RA (n = 9) or the RV (n = 13) in 22 juvenile sheep (22-56 kg). The catheter was deployed for 0.1-4.1 hr (RA) and 0.3-3.9 hr (RV). In 20 of these 22 animals, 32 recordings were made of filtered (30-250 Hz) bipolar electrograms and surface ECG. Electrograms were timed and used to construct activation sequences based on a schematic of catheter geometry. Hearts were examined either acutely (4 RA and 9 RV studies) or 4-8 weeks after the procedure (5 RA and 4 RV studies). One animal undergoing RA placement had an air embolism resulting in cardiac arrest immediately prior to basket placement; all other animals were stable during placement. RA electrograms of sufficient quality to determine activation time were recorded from 82% of pairs in RA maps, and RV electrograms from 89% of pairs in RV maps. Mean activation sequence duration in RV was 16 ms versus 47 ms in RA (P < 0.0001), making construction of RV maps more difficult. Acute postmortem studies of RV placement revealed a silent apical RV puncture in one animal. Superficial abrasion or ecchymosis of RV endocardium and/or tricuspid valve were noted in six animals. Postmortem exams in both RA and RV chronic studies showed healed endocardial lesions, with only superficial scarring. Rapid RV activation mapping using a basket catheter is feasible, but requires precision recording techniques. Endocardial abrasions produced in lambs both by RA and RV placement of the catheter are healed in < 4-8 weeks, with trivial residua. The multielectrode basket catheter may be applicable to the mapping of tachycardias originating in or involving the right ventricle.

Objective features of the surface electrocardiogram during ventricular tachyarrhythmias.

The aim of this study was to quantify the electrocardiographic signal characteristics of three types of ventricular arrhythmia; monomorphic ventricular tachycardia, polymorphic ventricular tachycardia and ventricular fibrillation. Patients in a coronary care unit were monitored using a single bipolar ECG lead. Thirty episodes of ventricular tachyarrhythmia (ten from each group) were recorded automatically by computer. Frequency analysis of ten consecutive 1 s epochs from each recording gave 100 spectra for each tachyarrhythmia group. Each spectrum was characterised by the frequency, there were significant differences in all characteristics between the tachyarrhythmia groups (P<0.025). Ventricular fibrillation had a higher mean dominant frequency (4.8 Hz) than polymorphic ventricular tachycardia (3.7 Hz) and monomorphic ventricular tachycardia (3.8 Hz). The dominant frequency of ventricular fibrillation was also more variable than that of monomorphic ventricular tachycardia (P<0.01). Mean peak size was largest for monomorphic ventricular tachycardia (0.78) and smallest for ventricular fibrillation (0.64). The single spectral peaks seen throughout this study indicate that all three tachyarrhythmias have an underlying periodic mechanism. The differences in spectral characteristics show that varying degrees of myocardial electrical organisation can be quantified from surface ECG features.